Will Big Istanbul Tunnel Help Traffic Problem?

Big Istanbul Tunnel is one of the biggest investments for the traffic problem of Istanbul. But will it help? Let’s look at the numbers.

The new metro of the tunnel will have a capacity of 75k/hour in one direction. That’s same capacity with Marmaray. But Marmaray did not cause any change in bridges so far. Daily ridership in Marmaray is 130k, 11% of all crossing Bosphorus. Marmaray is mainly attract sea passengers than car passengers.

The biggest advantage of Big Istanbul Tunnel is the route. The line is going through the most crowded regions of Istanbul. Metrobus, sharing the same route has a daily ridership of 800k. Going on special lanes except Bosphorus bridge, metrobus became a strong competitor of cars. By a faster and more comfortable service, metro will surely get most of the share of metrobuses and buses (19%).

Furthermore, the strong connections of new metro to other rail systems is another big advantage. Marmaray currently has one connection in Asian side, two connections in European side. This new metro will have nine connected rail system. That will be one of the strengths of this metro for reaching to daily ridership of 1.5mn.

But is there really a demand of 1.5mn for crossing Bosphorus through this tunnel? Currently 1.6mn passengers are crossing Bosphorus. Even only this metro may be sufficient for all. However plans are prepared not for today. The passengers to cross Bosphorus are expected to reach to 4 mn in 2023.

Some of the criticisms focus on this. New big investments to Istanbul will cause increase in population where Istanbul cannot live even with current population, so told by some authorities.

But question marks are generally focus on road part of the tube. 2 lanes will be constructed in each direction. And tube connecting TEM highway from two points will have a daily capacity of 120k cars. Today 420k cars are crossing Bosphorus every day. Considering the 3rd bridge under construction, bridges may be less crowded for a while. “For a while”, because every additional capacity for cars calls additional traffic soon after. Unfortunately, car is still the most comfortable mode in this pedestrian unfriendly city.

Another risk for road part of the tube is the congestion in TEM highway. Speeding up the Bosphorus will cause faster congestion in highway, and may end up with again congestion in tube. Connection to currently under construction North Marmara Highway may be a solution. But still we may start discussing two-storey TEM soon after the tube.